Humanist Discussion Group, Vol. 14, No. 114.
Centre for Computing in the Humanities, King's College London
Date: Fri, 14 Jul 2000 07:45:00 +0100
From: "Dr Donald J. Weinshank" <firstname.lastname@example.org>
Subject: Measuring the height of a building with a barometer.
The following charming story has been circulating in print and via E-mail
for decades, but, recently, has developed a new twist.
Great Moments in Physics
The following concerns a question in a physics degree exam.
"Describe how to determine the height of a skyscraper
with a barometer."
One student replied:
"You tie a long piece of string to the neck of the
barometer, then lower the barometer from the roof of
the skyscraper to the ground. The length of the string
plus the length of the barometer will equal the height
of the building."
This highly original answer so incensed the examiner
that the student was failed. The student appealed on
the grounds that his answer was indisputably correct,
and the university appointed an independent arbiter to
decide the case. The arbiter judged that the answer
was indeed correct but did not display any noticeable
knowledge of physics. To resolve the problem it was
decided to call the student in and allow him six
minutes in which to provide a verbal answer which
showed at least a minimal familiarity with the basic
principles of physics.
For five minutes the student sat in silence, forehead
creased in thought. The arbiter reminded him that time
was running out, to which the student replied that he
had several extremely relevant answers, but couldn't
make up his mind which to use.
On being advised to hurry up the student replied as
"Firstly, you could take the barometer up to the roof
of the skyscraper, drop it over the edge, and measure
the time it takes to reach the ground. The height of
the building can then be worked out from the formula H
= 0.5g x t squared. But bad luck on the barometer."
"Or if the sun is shining you could measure the height
of the barometer, then set it on end and measure the
length of its shadow. Then you measure the length of
the skyscraper's shadow, and thereafter it is a simple
matter of proportional arithmetic to work out the
height of the skyscraper."
"But if you wanted to be highly scientific about it,
you could tie a short piece of string to the barometer
and swing it like a pendulum, first at ground level
and then on the roof of the skyscraper. The height is
worked out by the difference in the gravitational
restoring force T = 2 pi sqroot (l / g)."
"Or if the skyscraper has an outside emergency
staircase, it would be easier to walk up it and mark
off the height of the skyscraper in barometer lengths,
then add them up."
"If you merely wanted to be boring and orthodox about
it, of course, you could use the barometer to measure
the air pressure on the roof of the skyscraper and on
the ground, and convert the difference in millibars
into feet to give the height of the building."
"But since we are constantly being exhorted to
exercise independence of mind and apply scientific
methods, undoubtedly the best way would be to knock on
the janitor's door and say to him 'If you would like a
nice new barometer, I will give you this one if you
tell me the height of this skyscraper'."
This is a lovely example of "thinking out of the box" and has been
Recently, however, I have received several copies of the story with two
1. The story is set at the University of Copenhagen.
2. The following "tag line" has been added:
The student was Niels Bohr, the only person from
Denmark to win the Nobel prize for Physics.
If true, this would not be entirely surprising. After all,
the battles between Bohr and Einstein at
the Solvay conferences in the late '20's hinged
on such "gedankenexperimenten" covering their
disagreements. Bohr was one of the champions of
quantum mechanics. Einstein always felt that "God
does not play dice" and that there had to be a deeper,
underlying mechanism, not simply random chance.
Be that as it may, can anyone authenticate the story
as being attributable to Bohr?
Dr. Don Weinshank email@example.com
Phone (517) 353-0831 FAX (517) 432-1061
Computer Science & Engineering Michigan State University
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